Imidazolium salts catalyst immobilization

Another substituted derivative of BINAP was used by Lemaire et al. [109]. The ammonium salt catalysts (7 and 8, Fig. 41.10) were prepared in situ from the bro-mohydrates and [Ru( /3-2-methylallyl)2(/72-COD)], and immobilized in several ionic liquids. By comparative studies of the hydrogenation of ethyl acetoacetate, the best results were obtained with imidazolium- and pyridinium-containing ionic liquids. No significant ee was observed with the phosphonium salt. This observation was attributed to problems of solubility and to the ability of complexation for the phosphonium ion. From the anionic side, use of the [BF4] anion appeared superior compared to [PF6] and [(CF3S02)2N]A... 

An ionic liquid was fully immobilized, rather than merely supported, on the surface of silica through a multiple-step synthesis as shown in Fig. 15 (97). A ligand tri(m-sulfonyl)triphenyl phosphine tris(l-butyl-3-methyl-imidazolium) salt (tppti) was prepared so that the catalyst, formed from dicarbonylacetylacetonate rhodium and the ligand (P/Rh = 10), could be soluble in both [BMIMJBFq and [BMIM]PF6. The supported ionic liquid-catalyst systems showed nearly three times higher rate of reaction (rate constant = 65 min ) that a biphasic system for the hydroformylation of 1-hexene at 100°C and 1500 psi in a batch reactor, but the n/i selectivity was nearly constant the same for the two ( 2.4). Unfortunately, both the supported and the biphasic ionic liquid systems exhibited similar metal leaching behavior. 

A benzene imidazolium-tagged ruthenium complex immobilized in [G4GiGiIm]PF6 is a highly enantioselective IL biphasic transfer hydrogenation catalyst (isopropanol/KOH) of acetophenone as compared with conventional (untagged) complexes (Figure Along the same lines, a diimide-imidazolium salt moiety associated with... 

In 2011, the same group reported the immobilization of an enantiomerically pure imidazolium salt derived from chiral binaphthyl on the surface of magnetite Fe304 and the formation of two catalysts derived thereof - a molecular Pd complex 84 and Pd NPs 85 (Scheme 3.47) [73]. These two catalysts were successfully... 

Other immobilized NHC-based rhodium catalysts targeted for screening in hydroformylation were synthesized by groups of Luis and Trzeciak (Scheme 2.166) [58, 59]. In the first step, Merrifield resin was functionalized to the corresponding bis(hydroxyethyl)amine derivatives. This material was converted into the corresponding dichlorides by chlorination with thionylchloride. Addition of an excess of 1-methylimidazol produced the immobilized bis-imidazolium salt. A... 

It is interesting to explore the structure when an organometallic complex is involved in the supported IL thin film. Catalyst models were prepared by immobilization of [Pd(DPPF)-(CF3C02)2] (DPPF, l,l -bis(diphenylphosphino)ferrocene) and CF3SO3H in imidazolium salts [(MeRR lmljfCFjSOj] supported on silica (R=H, Me R = Et, Bu, and hexyl) [62]. For comparison, a series of reference... 

ILs have also been designed to be Brmsted acids by covalently tethering an aUcanesulfonic acid group to the imidazolium or phosphonium cation of the IL The synthetic approach consists in the synthesis of a zwitterion in a first step then in a second step the zwitterion is acidified (Scheme 1) [20]. These salts are very viscous liquids. They can be used as both solvents and catalysts, or as functionalized Br0nsted acids that can be immobilized in more classical ILs. 

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